1. Field of the Invention
The present invention relates to cement and concrete products in general, and in particular to methods for making cementitious compositions having cement, gypsum, sand and/or gravel and water as ingredients thereof. More particularly, the cementitious compositions have one or more of a range of additives which produce final compositions, adjusted in terms of setting spread, strength, shrinkage and so forth, to fit prescribed specifications. More particularly still, the present method and product are suitable for application to the mining and like industries and provide fast setting, high strength and low rebound shotcrete. (For purposes of economy of nomenclature the shotcrete of the present invention will be termed "Suncrete", which is a trade mark of the assignee of the present invention).
2. Prior Art of the Invention
In the Dictionary of Civil Engineering (Penguin, 1991), the entry under "shotcrete" reads:
"Gunite with aggregate larger than 10 mm, a development of the late 1950s from the NATM (new Austrian tunnelling method) for lining tunnels in two stages, using shotcrete immediately after blasting, with aggregate up to 30 mm and an accelerating admixture. Steel mesh has been used to strengthen the shotcrete, and sometimes roof bolts also, but some users have replaced these by steel-fibre reinforcement. The mix can be made to set in as little as 15 minutes, providing safe cover for workers in large excavations such as the Milan-Rome motorway, 24 m (79 ft) wide, driven in the 1960s." PA1 (a) mixing together at least one ingredient from a first basic group of ingredients comprising: all sulpho-aluminate cement clinkers and other high alumina cement clinkers, at least one ingredient from a second basic group of ingredients comprising: gypsum; anhydrite; hemihydrate gypsum, and at least one ingredient from a third basic group of ingredients comprising: lime and hydrated lime; PA1 (b) adding to the mixture in (a) with a ratio not exceeding 20% by weight at least one additive ingredient from a first group of additive ingredients comprising: tartaric acid; tartarate-salts; boric acid; borate-salts; carbonates; lignosulphonates; sugars; molasses; citric acid; citrate-salts; and sulphonates, and/or at least one additive ingredient from a second group of additive ingredients comprising: all alkalis; strong base-strong acid salts; strong base-weak acid salts; lithium salts; lithium compounds; fluoride salts; chloride salts; and sulphonates; and PA1 (c) all mixing and adding in (a) and (b) performed in any order in predetermined proportions to yield said intermediate cementitious mixture. PA1 (a) a mixture of at least one ingredient from a first basic group of ingredients comprising all sulpho-aluminate cement clinkers and other high alumina cement clinkers, at least one ingredient from a second basic group of ingredients comprising: gypsum; anhydrite; hemihydrate gypsum, and at least one ingredient from a third basic group of ingredients, comprising: lime and hydrated lime; and PA1 (b) with a ratio not exceeding 20% by weight of the mixture in (a) at least one additive ingredient from a first group of additive ingredients comprising: tartaric acid; tartarate-salts; boric acid; borate-salts; carbonates; lignosulphates; sugars; molasses; citric acid; citrate-salts; and sulphonates, and/or at least one additive ingredient from a second group of additive ingredients comprising: all alkalis; strong base-strong acid salts; strong base-weak acid salts lithium salts; lithium compounds; fluoride salts; chloride salts; and sulphonates.
"Gunite", as distinct from shotcrete, is defined as having aggregate smaller than 10 mm, while shotcrete uses aggregate larger than 10 mm. In this specification, however, the term "shotcrete" will be used to include all classes irrespective of aggregate size.
Several United States patents are directed to shotcrete, spray concrete compositions, and the like.
U.S. Pat. No. 4,804,563 granted Feb. 14, 1989, to Hillemeier et al. discloses a spray concrete composition which is sprayed with driving-air pressure having its setting time accelerated by incorporation in the driving air of amorphous silica dust having an inner surface (specific surface area) of at least 25 m.sup.2 /g.
U.S. Pat. No. 4,931,098 granted Jun. 5, 1990, to Danielssen et al. discloses a method for adding silica fume to a dry shotcrete mixture wherein the silica fume is added together with the water supplied to the dry mixture in the spray nozzle.
U.S. Pat. No. 5,076,852 granted Dec. 31, 1991, to Bloys et al. discloses a cement method and composition for cementing a well penetrating subterranean formations and aqueous based drilling fluid containing at least one cement retarder characterized by a major proportion of the drilling fluid from the well as it was drilled; water; a lesser proportion of dry cementitious material; a minor amount of a dispersant that does not effect satisfactory set cement within an acceptable time interval; and an accelerator selected from the class consisting of acetic acid; the first 4 carbon esters thereof; acetamide; monoethanolanine; and diethanolamine. The first 4 carbon esters are the methyl; ethyl; propyl, both normal and isopropyl; and butyl ester, normal, isobutyl and teriy butyl.
U.S. Pat. No. 5,149,370 granted Sep. 22, 1992, to Olaussen et al. discloses cement compositions which have improved properties such as increased stability, reduced settling tendencies, enhanced, fluid loss properties and the like and method of using such cement compositions are provided. The cement compositions are comprised of water, hydraulic cement and an aqueous colloidal silicic acid suspension wherein the colloidal silicic acid particles have a specific surface area in the range of from about 50 m.sup.2 /g to about 1000 m.sup.2 /g.
U.S. Pat. No. 5,158,613 granted Oct. 27, 1992, to Sargeant et al. discloses hydraulic high density cement slurry, especially for cementation of oil/gas wells. The slurry contains 30-45 weight % microsilica based on the cement weight and water to a density of 1.9-3.5 g/cm.sup.3. if desired there can be added dispersant, retarder and weighting agent. Microsilica acts as a fluid-loss preventing agent. The addition of microsilica prevents strength retrogression at temperatures above 120.degree. C. and acts as a mechanical stabilizer for the cement slurries. A method for production of the cement slurry is also described.
U.S. Pat. No. 5,234,497 granted Aug. 10, 1993, to Crocker discloses a fast setting cementitious composition which upon hydration with water forms a paste-like slurry useful in stopping leaks in the walls of cement pipes. The cementitious composition comprises a dry mixture of a hydraulic cement component having a first Portland cement constituent and a second calcium aluminate constituent, an aggregate component and a lime component. Upon hydration with 23 wt. % water, the resulting slurry has an initial Vicat setting time within the range of 1-5 minutes and a final Vicat setting time of no more than 6 minutes. The cement component contains the first and second cement constituents in weight ratios within the range of 3:2-2:3. The lime component is present in an amount within the range of 1-4 wt. %
In effecting the repair of a water leak, a paste-like slurry is formed from water and the dry cementitious composition. The cementitious paste is supplied to the repair site. Sufficient force is applied against the paste to hold it against the repair site while allowing the cement to set to provide sufficient strength to offset the hydraulic gradient and stop the water leakage.
U.S. Pat. No. 5,273,579 granted Dec. 28, 1993, to Tanaka et al. discloses a quick setting composition capable of obtaining satisfactory strength developability irrespective of the fluctuation of the ingredients in a metallurgical slag, excellent in the strength developability at cold temperature, easy for coagulation control and inexpensive as well, which contains a cement ingredient comprising portland cement and/or mixed cement, 2 to 50% by weight at the integral ratio of a quick setting agent prepared by adding 3 to 20% by weight of an alkali carbonate at an internal ratio to a mixture comprising 40 to 95% by weight of a finely powdery metallurgical slag and 5 to 60% by weight of II-type anhydrous gypsum, based on the cement ingredient, and 0.1 to 5% by weight of a coagulation controlling agent comprising an organic acid type coagulation retarder and an alkali sulfate and/or calcium salt based on the total weight of the cement ingredient and the quick setting ingredient. U.S. Pat. No. 5,389,144 granted Feb. 14, 1995, to Burge et al. discloses admixtures for spray concrete or mortar which contain silicic acid sol or consist of it, are used for the processing of spray concrete or mortar according to the dry or the wet method. Said admixtures lead to a clear reduction of dust formation and of rebound. With the processing of spray concrete or mortar the addition of the inventive admixtures takes place preferably during the spraying, for example at the spray nozzle.
U.S. Pat. No. 5,413,819 granted May 9, 1995, to Drs discloses that the storage and processing times of sprayed concrete can be significantly extended by the addition of a retarder, a chemical compound which is capable of chelating with chemical ions. Preferred retarders are phosphonic acid derivatives which have at least one amino and/or hydroxyl group. The retarder can be used for both wet- and dry-sprayed concrete, the usual accelerators can be used for activation, and the strength is not adversely affected.
U.S. Pat. No. 5,401,538 granted Mar. 28, 1995, to Perito discloses sprayable fireproofing compositions for structural members such as steel columns are provided, as well as a method of applying multiple coatings thereof. The compositions comprise a Portland cement-based material, stucco, a high density aggregate and an accelerator. The compositions eliminate the long setting times typical of Portland cement-based materials, and improve the hangability thereof. The product is produced by dry blending a mixture of Portland cement, a high density aggregate, stucco (calcium sulfate and hemi-hydrate) and optionally, a stucco set retarder and shredded polystyrene aggregate. Upon the addition of water, sprayable slurries are formed which can be pumped to the point of application. An accelerator is added in close proximity to the point of injection. The slurries adhere to the structural member in the slurried state and after setting to provide excellent fire and heat protection. Because of the relative quick setting time of the slurry upon spray application, multiple coatings can be applied within the same working day.
Chinese Patent Application No. ZL90103141.0 filed in 1990 discloses high water content (90% water by volume) cementitious slurry for filling and stowing in mines uses cement clinkers such as sulpho-aluminate cement clinker, sulpho-ferrite-aluminate cement clinker, sulpho-fluo-aluminate cement clinker and other aluminate cement clinkers. However, such slurry is not suitable for use in shotcrete and the like applications. The major minerals in these cement types are:
______________________________________ sulpho-aluminate cement: 3CaO.3Al.sub.2 O.sub.3.CaSO.sub.4 -.beta.-2CaO.SiO.sub.2 ; sulpho-ferrite-aluminate cement: 3CaO.3Al.sub.2 O.sub.3.CaSO.sub.4 -.beta.-2CaO.SiO.sub.2 and 4CaO.Al.sub.2 O.sub.3.Fe.sub.2 O.sub.3 ; sulpho-fluo-aluminate cement; 3CaO.3Al.sub.2 O.sub.3.CaSO.sub.4 -.beta.-2CaO.SiO.sub.2 and 11CaO.7Al.sub.2 O.sub.3.CaF.sub.2 ; high-alumina cement: CaO.Al.sub.2 O.sub.3 and 12CaO.7Al.sub.2 O.sub.3 ______________________________________